The present invention relates generally to a lenticular lens array for producing visual effects from interdigitated or interlaced images. More particularly, the present invention relates to a lenticular lens array where a cross section of each lens element on the array comprises an elliptical shape. The present invention also relates to a tool and a method for creating such a lenticular lens array.
A lenticular lens can create visual animated effects for interdigitated or interlaced (hereinafter xe2x80x9cinterlacedxe2x80x9d) printed images. The images can be printed using non-impact printing, known as masterless printing, or by conventional printing processes, known as master printing. Typically, a lenticular lens application comprises two major components: an extruded, cast, or embossed plastic lenticular lens and the interlaced printed image. The front of the lenticular lens comprises a plurality of lenticules arranged in a regular array, having cylindrical lens elements running parallel to one another. The back of the lenticular lens is flat and smooth. The interlaced images are printed on the flat, smooth backside of the lenticular lens. Exemplary methods for printing the images include conventional printing methods such as screen, letterpress, flexographic, offset lithography, and gravure; and non-impact printing methods such as electro-photography, iconography, magnetography, ink jet, thermography, and photographic. Any of the above printing technologies can be used in either sheet-fed or roll web-fed forms.
The interlaced images are viewed individually, depending on the angle through which a viewer observes the images through the lenticular lens elements. At a first viewing angle, a first image appears through the lenticular lens elements. As the lenticular lens is rotated, the first image disappears and another image appears through the lenticular lens elements. Viewing the images through the lenticular lens elements can create the illusion of motion, depth, and other visual effects. A lenticular lens can create those illusions through different visual effects. For example, the visual effects can comprise three-dimensions (3-D), animation or motion, flip, morph, zoom, or combinations thereof.
For a 3-D effect, multiple layers of different visual elements are interlaced together to create the illusion of 3-D, distance, and depth. For example, background objects are pictured with foreground objects that appear to protrude when viewed through a straight forward, non-angled view. For an animation or motion effect, a series of sequential photos can create the illusion of animated images. A viewer observes the series of photos as the viewing angle of the lens changes. Animation is effective in showing mechanical movement, body movement, or products in use.
For a flip visual effect, two or more images flip back and forth as the viewing angle changes. The flip effect can show before-and-after and cause-and-effect scenarios. It also can show bilingual messages, such as flipping from English to Spanish. For a morph visual effect, two or more unrelated images gradually transform or morph into one another as the viewing angle of the lenticular lens changes. Finally, for a zoom effect, an object moves from the background into the foreground as the viewing angle of the lenticular lens changes. The object also may travel from side to side, but usually works better in a top to bottom format.
FIG. 1 illustrates a partial cross section of a conventional lenticular lens array 100. The array 100 comprises lenticules 102, 104, 106. Each lenticule 102, 104, 106 comprises a cylindrical lens element 102a, 104a, 106a, respectively. Each lens element 102a, 104a, 106a operates to focus light on a back surface 107 of the array 100. In operation of the conventional array 100, multiple images can be printed on the rear surface 107. An observer can singularly view the images through the lens elements 102a, 104a, 106a by rotating the array 100.
Specific characteristics of each lenticule 102, 104, 106 will be described with reference to exemplary lenticule 104. Each lens element 102a, 104a, 106a has a circular cross section of radius R. The circular cross section corresponds to a desired circular shape 108 having the radius R. The lens element 104a comprises a portion of the circular shape 108. Lenticule 104 also has a distance t from a vertex of the lens element 104a to the rear surface 107 of the array 100. The lens element 104a has a lens junction depth d where it joins adjacent lens elements 102a, 106a. Finally, the material forming the lens array 100 determines a refractive index N of the array 100.
The relationship between the distance t, the radius R, and the refractive index N is given by the following equation:                     t        =                              R            ⁢                          xe2x80x83                        ⁢            N                                N            -            1                                              (        1        )            
As shown in equation (1), the thickness t and radius R are a function of the refractive index N, which is a function of wavelength of light. Accordingly, the lenticular lens elements can be optimized for a particular wavelength based on the wavelength that provides the best overall performance for the desired application.
Regularity of the array 100 can be defined by the separation or distance S between the vertex of adjacent lens elements. For the conventional cylindrical lenticular lens array 100, the maximum separation between the vertex of each lens element 102a, 104a, 106a is given by the following equation:
Smax=2Rxe2x80x83xe2x80x83(2)
A pitch P of the lenticules can be defined as a number of lenticules per unit length (lpu). For example, the unit length can comprise an inch or a millimeter. For the conventional cylindrical lenticular lens array 100, the minimum pitch is given by the following equation:                               P          min                =                              1                          2              ⁢              R                                ⁡                      [            lpu            ]                                              (        3        )            
FIG. 2 illustrates a light ray trace illustrating several problems associated with a conventional lenticular lens array 100. In general, the array 100 operates by passing light from the rear surface 107 through the lens elements 102a, 104a, 106a to an observer. Reciprocity allows viewing the light path in reverse as illustrated in FIG. 2. Ideally, on-axis light L1 passes through lens element 104a and is focused to a common point 202 on the rear surface 107 of the array 100. However, the circular cross-section of the lens element 104a produces a projected image having spherical aberration. For example, the light L1 is projected over a large area 204 on the rear surface 107. The large projection area limits resolution and the number of interlaced images that can be viewed on the rear surface 107.
Additionally, off-axis light L2 passes through the lens element 104a and is focused upon the rear surface 107 near point 203. However, the circular cross-section of lens element 104a produces coma and an astigmatic aberration 208. Finally, FIG. 2 illustrates that the depth d of the lens surface can approach the radius of the circular cross-section at the junction of adjacent lenses. Accordingly, portions of the light L2 are blocked by lens 106a and may be redirected to the wrong location 206.
FIG. 3 illustrates a light beam projection illustrating another problem associated with the conventional lenticular lens array 100. FIG. 3 illustrates light beams projected to an observer from different printed areas of the conventional lenticular lens array 100. As shown, the light beams in the central area 302 are not reasonably matched over the circular angle of the lens.
Furthermore, conventional lenticular sheet-fed printing has been used to create promotional printed advertising pieces printed on a lenticular lens array. For example, the advertising pieces include limited volumes of thicker gauge lenticular material designs such as buttons, signage, hang tags for clothing, point-of-purchase displays, postcards, greeting cards, telephone cards, trading cards, credit cards, and the like. Those thicker gauge lenticular printed products are printed on cylindrical lenticular material having a standard thickness. For example, standard thicknesses include 0.012 mil, 0.014 mil, 0.016 mil, 0.018 mil, and up to 0.0900 mil. Printed quality on those thicker lenses are generally acceptable because the lenticule pitch is more course (fewer lenticules) and the printing process can place more printed image pixels within the lenticule band range. Additionally, lenticular materials at the thicker ranges tend to be more optically forgiving then thinner gauges.
Recently, lenticular extruders, lenticular casting/embossers, and print manufacturers have experimented with decreasing the overall lenticular material thickness using the common cylindrical lens elements discussed above. However, as the thickness of the lenticular lens array decreases, the print quality suffers significant aberration. As the thickness decreases, lenticule pitch must increase to provide more lenticules per unit length, thereby reducing the separation between lenticules. That thinner configuration does not allow using as many printed pixel images when compared to the thicker lenticular material designs. Accordingly, the quality of the printed visual effects is degraded with the thinner material.
Another problem with thicker lenticular materials is that the thicker materials cannot be used for the majority of the consumer packaging industry. That problem arises because thicker materials of 0.012 mil and thicker cannot be applied nor handled properly to cylindrical or truncated package shapes without de-laminating off the package due to plastic memory pull. Even when a strong adhesive is used to bond the thick lenticular piece to the packaged unit, problems with de-lamination still occur over time due to the continual pull of the plastic material, as the plastic memory pulls the material to its natural, straight produced shape.
Thicker lenticular materials also experience problems during the label application process. Automated printed label blow-down or wipe-down packaging labeling equipment cannot apply the thicker lenticular materials, because of the plastic memory issues discussed above. The plastic memory causes the thicker lenticular die cut labels to rise off the lenticular label rolls before the application process.
Therefore, a need in the art exists for a lenticular lens array that can provide a more focused or resolved image by mitigating the spherical aberration associated with conventional arrays. A need in the art also exists for a tool and a method for making such a lenticular lens array. Furthermore, a need exists in the art for a lenticular lens array having a lenticular lens element shaped to mitigate the spherical aberration associated with conventional lenticular lens elements. A need also exists for a lenticular lens array having a thin structure to mitigate plastic memory issues associated with thicker, conventional arrays.
The present invention can provide a lenticular lens array that can optimize printed display quality of animated/three-dimensional images for mass production. The present invention can provide a lenticular lens array that can mitigate the spherical aberration typically produced by a conventional array. For example, the present invention can provide a lenticular lens array that can produce a substantially focused axial image and can improve the off-axis image. Additionally, the present invention can provide a lenticular lens array having a reduced lens junction depth, which can mitigate off-axis light blocking by adjacent lenses.
The lenticular lens array according to the present invention can comprise a plurality of lenticules disposed adjacent to each other. Each lenticule can comprise a lenticular lens element on one side and a substantially flat surface on an opposite side. Each lenticular lens element can have a vertex and a cross section comprising a portion of an elliptical shape. Alternatively, the cross section can comprise an approximated portion of an elliptical shape. The elliptical shape can comprise a major axis disposed substantially perpendicular to the substantially flat surface of each respective lenticular lens element. The vertex of each respective lenticular lens element can lie substantially along the major axis of the elliptical shape.
These and other aspects, objects, and features of the present invention will become apparent from the following detailed description of the exemplary embodiments, read in conjunction with, and reference to, the accompanying drawings.